Fuchs corneal dystrophy (FCD) is a common bilateral late onset disorder of the corneal endothelium chracterized by a slowly progressive dysfunction of corneal endothelial cells associated with the loss of these cells and the formation of excrescences (corneal guttae) and excessive thickening of Descemet's membrane. This age-related disorder has a striking female:male preponderance. Evidence for Mendelian forms of FCD comes from large multigenerational FCD families. However, the majority of FCD are found in small families, which exhibit a complex form of FCD. FCD has also been mapped to loci on several chromosomes. The objective of this application by an experienced multidisciplinary team of investigators is to expand family recruitment and further our understanding of FCD with genetic studies. This study has five specific aims: (1) To continue recruiting families of FCD with at least one affected individual and up to two unaffected siblings as well as multigenerational FCD families, (2) To sequence and genotype the COL8A2 gene in each affected individual, (3) To perform a whole genome linkage screen using Illumina's fourth-generation SNP-based linkage panel, (4) To perform association mapping for up to four linkage regions to identify candidate genes associated with FCD and to follow up of these candidate genes, and (5) To perform positional cloning for large multigenerational families. To achieve these goals, an ocular examination will be performed on all participants to determine whether they are affected or not. Families with COL8A2 mutations will be removed from the linkage and follow-up analyses. Linkage analysis will be performed on various datasets of families of different size. This strategy will allow chromosonal regions that are responsible for Mendelian and complex forms of genetics in FCD to be identified. The long-term objective of this study is to understand the basic pathobiology of FCD and to identify genetic components of the disorder that will be valuable from the standpoint of developing molecular diagnostic tests for early diagnosis and for developing novel therapeutic procedures for this debilitating disease. Statement of Relevance: Knowledge about the genes that place individuals at risk for FCD will lead to a better understanding of this important disease, early diagnostic tests and novel non surgical methods of treatment.